Systems in which the entire functionality of a macroscopic laboratory is accommodated on a plastic substrate, for example the size of a credit card, are referred to as a lab-on-a-chip (LOC). LOC systems are often used for microfluidic applications in which complex biological, chemical and/or physical processes can take place in a miniaturized form. Channels and cavities are necessary for this, in order on one hand to store the liquids in reservoirs and on the other hand to meter them with the aid of valves or control the timing of their release within the LOC system.
In many cases, LOC systems consist of a polymeric layer structure. In the simplest case, this structure consists of two polymer substrates, which comprise cavities in the form of chambers and channels. Between the polymer substrates there is a flexible polymer membrane film, which is provided as a membrane for the valve. In order to ensure the functionality of the LOC system, the necessary liquids must be either stored directly in the LOC chip (‘on-chip’) or be supplied from the outside by way of fluidic interfaces.
It is of advantage for many LOC applications to store the liquids that are necessary for the functioning of the chip ‘on-chip’. Fluid-tight reservoirs and valves are necessary for this, in order to prevent any loss of the liquids by diffusion from occurring even over lengthy storage times. The valve technology is in this case based on the pneumatic deflection of the polymer membrane film, in order to open or close valves. A disadvantage of this is that liquids that are pre-stored on the chip cannot be stored in a fluid-tight manner without a pneumatic connection, since the valves are not closed in the basic state.
Furthermore, it is known from the prior art to enclose liquid reagents in a microfluidic system during the production process. In this case, for example, predetermined breaking points, which open when a predetermined pressure is reached and thereby allow the reagents to be released into the LOC, may be formed in the polymer-membrane composite.